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Species of Austrodanthonia on an acid soil on the southern tablelands of NSW

D. Garden, T. Brassil, C. Shields and R. Smith

NSW Agriculture, PO Box 1600, Canberra, ACT.

ABSTRACT

Austrodanthonia spp. were identified on an acid soil on the southern tablelands of NSW. Samples were collected in 9 broad areas over the site, reflecting the different combinations of slope, aspect and soil depth. Plants were grown in pots and ripe panicles collected for species identification. The most common species present were A. carphoides, A. racemosa and A. auriculata. Species which are normally regarded as productive (A. richardsonii, A. bipartita, A. fulva, A. duttoniana) were generally absent, with only one sample of A. duttoniana being found. The influences of topography and soil differences on the range of species present, and the implications for selection of cultivars of Austrodanthonia are discussed.

Key words

Austrodanthonia, species, acid soil, soil pH, ecotype, adaptation.

INTRODUCTION

Austrodanthonia species are some of the most important native perennial grasses in grazed pastures on the tablelands of NSW (3). Whether pastures have been sown to introduced species or not, a significant component of Austrodanthonia spp. is likely to be present. Previous studies have shown differences between Austrodanthonia spp. in their adaptation to different soils, grazing management and fertiliser regimes (4). However, in many agronomic studies, while Austrodanthonia is recorded as being present, individual species are rarely identified. In this study, Austrodanthonia spp. present on a soil on the southern tablelands of NSW that was acid to depth were identified. The species present were related to topographic and soil differences to determine the effects of soil factors on species distribution.

MATERIALS AND METHODS

The sampled site was at Sutton, NSW, 30 km north of Canberra. The 35 ha area had been selected for the establishment of an experiment on the use of lime to ameliorate soil acidity. The soil was derived from mixed granite and sedimentary parent material, and topography ranged from shallow skeletal ridges to deeper soils on lower slopes (Table 1). The site supported a pasture of mainly native perennial grasses (e.g. Austrodanthonia, Aristida, Austrostipa, Microlaena) with annual grasses, and small amounts of introduced legumes and grasses. Austrodanthonia plants were collected in 9 broad areas, reflecting the different combinations of slope, aspect and soil depth, and grown in pots for later identification. Areas, which were to be part of the lime experiment, had data available on soil pH, Al, Mn and P. however, plants were also collected from three relatively undisturbed areas outside the experiment, for which no soil data were available.

RESULTS

A total of 8 species of Austrodanthonia were found on the site (Table 1). The most common species present were A. carphoides, A. racemosa and A. auriculata. Species which are normally regarded as productive (A. richardsonii, A. bipartita, A. fulva, A. duttoniana) (1) were generally absent, with only a single sample of A. duttoniana being found. The species A. carphoides, A. auriculata, A. eriantha and A. pilosa were generally more common on the shallower, skeletal soils, while A. racemosa was most commonly found on deeper mid and lower slope areas. The range of soil conditions found on the site was limited, with pH ranging only from 4.11 to 4.27. However, there was a tendency for A. racemosa to be more common above pH 4.2 and A. pilosa and A. auriculata to be more common at lower pH. The main difference in soil characteristics was in Mn. In area E (Table 1), soil Mn was much higher than at any other location. The dominant species in this area were A. pilosa and A. auriculata.

Table 1. Topography, soil data, dominant perennial grasses and Austrodanthonia species present at nine locations on a deep acid soil on the southern tablelands of NSW (most common species underlined).

Area

Topog-raphy

pH
(CaCl2)

Al
(mg/kg)

Mn
(mg/kg)

P
(mg/kg)

Dominant
perennials

Austrodanthonia spp. present

A

Western gravelly ridge

4.20

1.5

6.4

5.3

Austro-danthonia, Aristida

carphoides, racemosa

C

Eastern skeletal ridge

-

-

-

-

Aristida

eriantha, carphoides, auriculata, pilosa

D

Western lower slope

4.27

0.9

10.6

5.8

Austro-danthonia, Phalaris

racemosa, carphoides

E

Shaley mid-slope

4.11

1.7

49.6

5.0

Austro-danthonia, Digitaria

pilosa, auriculata, setacea, monticola, duttoniana

F

Western facing ridge

4.16

2.2

7.0

6.0

Austro-danthonia, Aristida

auriculata, carphoides, racemosa

H

Skeletal ridge

-

-

-

-

Austro-danthonia

pilosa, racemosa, eriantha, auriculata, setacea, monticola

I

Eastern lower slope

-

-

-

-

Themeda, Austro-danthonia

eriantha, racemosa, pilosa, monticola, carphoides

J

Mid-slope

4.20

1.8

5.4

8.1

Austro-danthonia, Microlaena

racemosa, setacea, auriculata

K

North facing ridge

-

-

-

-

Austro-danthonia

auriculata, pilosa, racemosa, carphoides

DISCUSSION

The work of Dowling et al. (2) suggests that Austrodanthonia species which are better adapted to acid soils are A. pilosa, A. eriantha, A. duttoniana, A. setacea and A. monticola, and all these species were present at our site. In their study, A carphoides appeared to be independent of pH, and A. auriculata was uncommon. In the present study, both these latter species were found at most sites, suggesting that they must have some acid tolerance and be adapted to shallow soils. These species generally occur together in such locations on the southern tablelands of NSW. The situation with A. racemosa is more complex. Scott and Whalley (4) found no influence of soil pH and P level on occurrence of A. racemosa, whereas Dowling et al. (2) found that A. racemosa was more common at higher pH, and Bolger and Garden (1) found that A. racemosa had a higher requirement for N and P than many other Austrodanthonia species. In this study, A. racemosa was present at low pH sites and where P levels were low. This suggests that there may be a wide range of ecotypes of this species, as suggested by Scott and Whalley (4), allowing the species to be present in a range of environments. These results suggest that determining adaptability of different species of Austrodanthonia is not simple. However, it is important that this is appreciated, especially where selection of cultivars of this genus is being undertaken.

REFERENCES

1. Bolger, T.P. and Garden, D.L. 1999. Proceedings VI International Rangeland Congress, Townsville. Vol 1, 269-271.

2. Dowling, P.M., Garden, D.L., Eddy, D.A. and Pickering, D.I. 1996. NZ J. Agric. Res. 39, 619-621.

3. Garden, D., Jones, C., Friend, D., Mitchell, M. and Fairbrother, P. 1996. NZ J. Agric. Res. 39, 471-485.

4. Scott, A.W. and Whalley, R.D.B. 1982. Aust. J. Ecol. 7, 239-248.

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